Control apparatus for radio receivers



April 1950' R. c. MARHOLZ 2,503,058

CONTROL APPARATUS FOR RADIO RECEIVERS Filed April 6, 1946 2 Sheets-Sheet 1 FIG. I

INVENTOR. RICHARD C. MARHOLZ BY 37W ATTORNEYS April 4, 1950 v R. c. MARHOLZ 2,503,058

CONTROL APPARATUS FOR RADIO RECEIVERS Filed April 6, 1946 I 2 Sheets-Sheet 2 INVENTOR.

RICHARD C. M RHOLZ WI- 9/401) ATTORNEYS Patented Apr. 4, 1950 CONTROL APPARATUS LFORRADIO ancnrvsns v. Richard C. Marholz, Chicago,".lll.,.assignor .to Belmont,RadiofCorporation,Chicago; 111., a cor- .poration of Illinois :Application April 16, 1946;;Serial No. 660,028

The present. invention relates .to .control apparatus for radio 'receivers'or transmitters. and more particularly to..-manually operable automatic tuners :of..the mechanical type for such receivers or transmitters. .Specifically, the present invention is concerned with an-improve- .ment on U. S; LettersPatents 2,130,153, 2,154,406 and 2,172,288, all --assigned.'to: the same assignee as the present application.

Various push button actuated mechanical controlled devicesare commercially available for selectively controlling the tuning elements.=.- f radio receivers. Ingeneral, suchmechanical-control devices or automatic tunerscomprise' a series ofmanually operable push buttons which" enable the listener to "selectively tune 'in'particular stations merely by pushing. on actuating the push buttons. Inaddition, the receiver usuallyineludes manual means for tuning it to. any other broadcasting. station within; the rangeof the receiver in addition. to-.those for-which the automatic tuning arrangement,-;including. the push 'buttons,'is set. .In oneform of. automatic tuner for radio receivers, a series: of variably positioned cams are provided along the shaft, one for each of the push bottons. Suitable means. are provided for. holding these/cams vinpredetermined positions relative to. the .tuningv-shaft so:.:,that when a push buttonis actuated, .its'associated cam is' rotated with the consequent rotationof the tuning shaft'to a' predetermined positioncorresponding. tothe particular-station setting for which the push button and: associated cam .have been adjusted.-. In orderinitiallyto set the automatictuning arrangement or to change the'setting thereof, vit-is1necessaryeto,producerelative movement between the cam and the tuning. shaft after which the cam is locked: to the shaftinfa perdetermined position-relative thereto.

In the tuning: arrangements. disclosed-in the above-mentioned patents the cams vor -contro1 members are positionedwalong the; tuning shaft in. between frictional: means. and suitable spacing sleeves are providedbetweeni .-the' frictional ineans associated I with adjacent cams or control means.

The camsarelocked tmthe shaft -by.-. applying a compressiveiforce toithe-end oilthestack of cams, frictional meansthet-spacersarranged on the tuning shaft :and .generallysreferred teas the cam stackpwhereupon.each:cam1.is.irictionally held betweeniits frictionalemeans, generally comprising apair. of washers, sone-on eitherJsi-de of the cam which are. mounted on the shaft ;.-in such a manner thatrrelativerotation with respect to the shaft is-prevented. A suitable man- .ually operable tuning-knob. at theeendtof the tuning shaft for rotating' thetsame is commonly employed. Heretoforet in order "to apply a .com-

pressive force-to the-.-cam. stack,..it was; general 3'Claims. (01174- 1035) practice .to provide .a .screw extending through thentuning. knob. .Tlhis, screw was. operable by :meanspf a.screw,..driver.applied from. the front ,of. the tuning knob. .Although this arrangement ..has.-fbeen found .to .bevery. satisfactory,- it is always. necessary. .to. .employ tcols such as a screw driver. or the like-.bothfor initially tuningtheset and. to subsequently change these settings.

It.- is .an. objectof. the present invention to .p ,vicle. a new. and ..improved ..automatic tuning .ar-

.rangement inwhi-ch no ,tools need be .employed .f0r.,.chang'ing.the station settings. ,as. controlled by the. pushbuttons.

It isanotherobject of thepresent invention to .provide an automatic, tuning :mechanism which .Lcan -hesetland. reset merely .by axial movement of: the manuallyrotatable. tuning. knob without .thereqinrement. ,ofextra tools or. equipment.

.It is a further. object of; the. present-invention to provide .a.new..;and improved manuallyoper- ...able automatic tunerifor radiov receivers having a:- pl-nra-lity-of control elements on a rotary shaft with -;the,.control elementsadapted to be simultaneously. locked-to the. control shaft solely .by

..manipulation. of a tuning; knob.

. Still .another objectv .of the present, invention is :to :provide a: new. and, improved automatic tuning mechanisrnin which taxi-a1: movement of .,.-the.tnning;kr10b controls the pressureapplied to the-camstack.

- Furtherrobjects. and. advantages of the present .invention wi1l.,-become ,apparent .as they follow- -ing description proceeds and the featurest of novelty which characterize the present invention -.will:-.be' ;p0inted outwith particularity, in the ..c'laims,.annexed.to and forming a parteof this For-a better understanding; of the present inventionn reference-maybe had,to' the accompanying drawings in which:

l-is aperspective view of a radio receiving. set'embodying the-present invention;

vFigL2-is an enlargedperspective and somewhat USGhGHIQJtiCwV'iBW; partlygin section: o-f ,the tuning "mechanismwof -,-t-he;-. present. invention; employed -.&-.Elg.- 3- is a" sectional View :of the tuning knob and. a.-portionxof;the1 cam-stackof Figs. .1 and 2 .with the cam shown in locked condition;

Fig.- 4sis the sectionalviewesimilarvto Fig 3 =s-ShOWlllg the. tuning--knoband aaportion of. the

steam. stackrw-ith,-the=.-cams in :the .unlocked condivtion: .to permit-relative I movement between the control. members or JcamS and'the tuning shaft;

and

Fig. 5 is a sectional. viewtaken onrline 5-5 of Fig. 3'.

.. Althougha..the ...present invention, adaptable -.for ...use-awith v any-aapparatus.employing. tuning mechanisms such as radio receivers or radio transmitters, it is especially adaptable for use with radio receivers employing a relatively small cabinet, often referred to as a midget receiver and the invention has been specifically illustrated in connection with such application.

Referring now to the drawings, there is illustrated in Fig. l a radio receiver generally indicated at Ill, comprising a cabinet ll of any conventional style. A suitable tuning knob I2 is provided for manually tuning the receiving set Ill and in addition, a plurality of push buttons 13 are also provided which may be used to tune in certain specific stations to which the set is frequently tuned.

The tuning mechanism for the radio receivin set IU of Fig. 1 comprises a rotary tuning shaft 14 which is suitably journalled in frame members I and i5 supported from a base member H. The rotary shaft l4 which is provided with a longitudinally extending keyway l8, best shown in Figs. 2, 3 and 4 of the drawings, is coupled or otherwise suitably connected to a resonant frequency changing means or a frequency control device for tuning the radio receiver to particular stations. This resonant frequency changing means may comprise a variable inductance or a variable condenser and has been illustrated in Fig. 2 of the drawings as comprising a variable condenser l9 having a plurality of rotor plates fixedly mounted for movement with the rotation of the shaft I4, and a plurality of stator plates 21. The rotor portion of condenser I9 is rotatable through an angle of substantially 180 degrees. Rotation of the tuning shaft M will cause the capacitance of the variable condenser 19 to vary with the resultant tuning of the radio receiving set I!) to any desired station within the range of the receiver. The tuning knob 12 mentioned above is associated with the shaft 14 at the end remote from the condenser I9 in a manner which will be described in greater detail hereinafter. In any event, rotation of the knob l2 causes rotation of the shaft M.

In accordance with the now well-known automatic mechanical tuning mechanisms such as are disclosed in the above-mentioned patents, the shaft I4 is also controllable in so far as rotation thereof is concerned by the plurality of push buttons l3 mentioned above, whereby particular stations to which the listener frequently desires to listen may be tuned in merely by actuating one of the push buttons which automatically causes the desired location to be imparted to the shaft M without further effort than to actuate one of the push buttons.

It should be understood that each push button l3 may be associated with a selector unit comprising a slidable member which is moved in a longitudinal direction upon the actuation of push button l3. As illustrated in the drawings, however, each of the push buttons l3, only one of which is shown in Fig. 2 thereof, is associated with an L-shaped lever or member 22 having a notched-out portion 23 adapted to be slipped over and pivotably mounted on a support or shaft 24 which in turn is supported between frame members l5 and I6. As was mentioned above, in order to simplify the disclosure, only one such push button and L-shaped member is shown in Fig. 2 of the drawings, but it will be understood that a series of such levers or members 22 will be provided along the support 24 which may be spaced in any desired manner, such as by suitable spacing sleeves 25. The portions of the shaft l4 and the support 24 which have been omitted from Fig. 2 of thedrawings are shown in dotted lines and the associated push buttons and other members have been completely omitted.

In order to hold the L-shaped lever 22 in position for pivotable movement relative to the support 24, there is provided a spring member 26 which is of one piece, hairpinlike construction, comprising a hooked end 2611 which extends over the top edge of the L-shaped lever 22 with a bowed retaining portion 26b passing beneath the support 24 and extending to a looped portion 260 hooked over the top edge of the L-shaped lever 22 to the rear of the support 24. The spring 26 is also provided with an extension 2601 which engages the base I! of the chassis to maintain the L-shaped lever 22 in the position indicated in Fig. 2 of the drawings except when 'a force is applied to the push button portion 53. The end of the L-shaped lever 22 remote from the push button I3 is provided with a roller 2'! pivotably attached thereto by means of a pin or a stud 28. If desired, this roller 2! may be dispensed with and instead the end of the L-shaped lever 22 may be merely a rounded projection or the like.

In order that different desired station settings may be imparted to the tuning shaft 14 by means of the push buttons [3, the selector units comprising the series of L-shapecl levers 22, only one of which is shown in Fig. 2 of the drawings, are each adapted to engage the edges of cooperating selecting or control members comprising heart-shaped cams 29. Each heart-shaped cam 29 is provided with an opening for accommodating the tuning shaft I4 and is normally held in a fixed relative position therewith, which position may be varied by means to be described hereinafter. Also, each cam 29 is positioned on shaft [4 so that the edges thereof are engageable by the roller 21 of its associated L-shaped lever 22. Furthermore, each of the cams .29 is positioned between a pair of washers 30 and 3! at least one of which is provided with a cooperating extension 32 for sliding in the keyway l8 whereby at least one of the Washers 39 or 3| is non-rotatably positioned on the shaft [4. Preferably the Washers 39 and 3| are identical and comprise a pair of shoulders 33 engageable with a stop lug 34 illustrated as a punched-out portion of the heartshaped cam 29. This stop lug 34 is provided on only one side of cam 29 and serves to limit the relative movement of cam 29 and shaft Hi to substantially degrees. It will be understood that the shoulders 33 need not be provided on the washer 3| since no stop lug is provided on that side of the cam 29. However, in order to keep the number of different parts of the apparatus at a minimum, it is preferable to employ identical washers 39 and 3| on either side of the cam 29 which washers provide the frictional means for locking or holding the cam 29 in a fixed position relative to the shaft 14.

In order that the cams 29 may be held in spaced relationship along shaft l4, suitable spacing means or sleeves 35 are provided between the washers 39 of one cam and the Washer 31 of the adjacent cam. In addition, shaft M is provided with a stop member 36 near the end thereof adjacent to the variable condenser 19. The spacing means 35, the washers 39 and 3 l and the earns 29 are assembled on the shaft I4 from the end remote from stop 36. All these members are rotatable about the shaft I4 except the Washers 30 and 31 'which are keyed against rotation by k v djacent tot'he'end of the tunin I haft I 4 re o e from the i stop member 36, as is gweshe -s a"washer 38 and a bushing 39 1ch has a (portion of reduced cross-section dapted 'tofitf int'o 'an opening 40 in the frame ember 1'6. The' members 31, 38 and 39 are 16. In accordance with the present invention, fjsui'table means areprovided for compressing and releasing thefc'amwtack "solely in response to inbvement'of theknobflZrelative to the shaft i4 'fand pa'rticula'rly withreference to axial move- ?mentof the-knob I2. This means may comprise 'a [If-shaped spring member'or, as illustrated in i thedrawihgsga pairof leaf spring members 4!. accommodatethese leaf spring members 4|, "portion ofthe' s'haftifat the end adjacent the ""k a "f V p vid'ed with-diametrically opposed arter es-surfaces "Hat and 14b which are illusitrate iesbeing displacedffrom the keyway I8 by degrees. 'This fporti'ono'ftheshaft 14 having fj'the flattened surfaces 14a and 'l4b extends jfthrough'anopening Hw inthe'cabi'net II wherebyfthe'knobl2 "may be positioned outside the *cabinet.

Topreveht the'1eaf"springs 4| from moving ialongthe'flatteh'ed "surfacesMa and 14b of the *shaft 14in a'direction away from the camstack, "the end of'the shaftl 4 ispreferably provided with a threadedopenin'gfl to accommodate a screw i4 3 ='*forholdihgawasher 44 against the 'end of fthe'shaft Mas is'learly shown in Figs; 3 and. 4 of thedrawings; screw 43 and washer may "'beffori'ned of insulatingmatrialif desired; where- "by the'possibility of obtaining a shock through "manipulationbi tii'ningknob I2 is completely eliminated. The knob] z i's'pro'vided with a shank f-po'r'tijon 45"ahd pi eferably the knob and shank are oldedbr' -otherwi'se formed from a suitable inating-material*such' as' aplastic or the like. janl gj45' ofthe knob IZis shaped so as to M Shaft 14 and a luranty of longierr e "I'm. ar d:

"tu dinal recesses 46 are 5 provided along part" of the shank as? is best'shjown in Fig; 5 of the draw- 'gs"to"accommodate the bowing action of the leaf springs 4l"-'as'will be described in greater dei' ii hereinafter. The recesses 46 do'not extend '"throu'ghout the whole length of shank '45 as is "fobvio'us *from Figs: 3 and/1 of the drawings, 'wiseret the solid portion of the" shank not provided withjthe re'qe se 46 "holds the leaf springs agains't'thefiattned surfaces Ma and Mb of the In order to'limit theoutward' movement of the knob I2, it"i'sprovided with-a'large central recess 41, the bottom of which is provided with a shoulder- V-portion 48 which engages with the e 11 permits r name mo ment betweenfthe mounted-en the ca m" side of the frame member washerflsna the "knelt l2. "when theknob l2 may expand-"and the" spring wasnerei may" help to controlfthe'initialfltension"applied tothe cam s'ta'ck. When" thekiiob I 2 on the other "hand: "is

moved the cabinet] 1, "the portion of the shank '45- not'providedwith the recesses '46 forcesthe-leafs ojrings are) moveagainst-the flatpbsitiohs on'shaft I4. This arrangement is'shown"in'Fig;'g of the drawings and it will' be observed that thefspring Washer 31" is wholly compressedfinthis position. -In'order that the leaf springsfl I" whose ends'engage the washer an and t e P s n 9 it a vel w r s. ni tb' m distribute the force-applied to the bushing 39, the ends"fthereof adjacent the bushing 39 *are provided 'withsubjstantially'fright angled extensions49. The 'aX'ialmovenientofthe-knob i2 "in the "direbtibnftoward the'cam stack -may be limited by any suitable means such, for example,

"ings, this stop means is indicated as'the' right angled persons-t9 which-engage the end-of the sh m t5, theknobj'gi z' b'ei'h' shown in its extreme 'inwa'rd'position-in 3 of thedrawings. I

In assemblingthe knob IIan'dIe'af springs-4|,

the leaf springsfare' placed on thshaft l4" and the knob 12 isslipped ov'er-the end ofthe shaft l with the" washer 44 "and the f screw' 43 removed.

The'initial tension tppn e tothe *cam'sta'ckmay thenbe adiustedby putting theleaf springs to I the proper-length er*byapplying-suitable shims "tothe'hd of shaft M btweenitand the washer 44. 'Iheinitial tehsibn should be such that the earthame cams-29 willrem'ainin a fixed position once they areadjusted, although they are relativelymovable with respect to shaft' l4 when anadjustingforce'is'applied thereto asby actuation of thepush'fb uttp'ns I3. "When this initial 'ten'sio" is'obtained'and the 'washer4'4 is fastened m dpanama-m ns"or screw '43, the cams zs "may be locked and'un locked merely byaxial move- ,ment' of l2; it"s ftwo extreme positions being shown-i'n- Figs. 3 and 4 respectively of the draw- 'ihgs. iin b'rder to besure that shaft is rotated upon rotation'of knobd2, it'may bedesirable to provide a suitable set screw such-as isindicated at 50 in Fig. 5 of the drawings which extends through theshank 45 of the knob 12 and into engage'ment with the keyway 18. By employing a set screw such as whichstill permits axial movement of the knob l2 rotation of shaft I4 is insured while permitting a fairly loose fit with shaft l4to permit axial movement of knob I2.

' It will be understood that various modifications of the spring'rneans 4|, the means for adjusting the initial tension and the stop means for limiting Y the axial movement of knob 12 may be employed.

several such modifications are disclosed in Royal "Patent No. 2,450,918, issued October 12, 194 8 'a'ssigned to the same assignee as the present application, a w i a The'o'peration of the tuning mechanism described thus far willbe obvious in view of the de- 70.

tailed description includedabove. Assuming that the members defining the cam stack are in positi-onfon the-tunin'g 'shaft l4-and the knob l2=is removed from the'e'nd of the shaft'l4 which is accomplished by re'r'novin'g' the screw 43 and the washer 44, the springs 4| are positioned onthe flattened surfaces Ma and Nb of the shaft I4 and the shank 45 of the knob I2 which is next placed in position holds the springs. To provide the desired initial friction, which compresses the cam stack a predetermined amount, the springs M are either cut to the proper length as mentioned above, or shims are employed between shaft I4 and washer 44 which permit the ends of the springs 4| to extend beyond the end of shaft I4. It is desirable that this initial friction be such that the cams 29, although rotatable relative to the shaft I4, when a small force is applied thereto by means of L-shaped levers 22 will with out such force remain in a fixed position relative to the shaft I4. As soon as this initial tension has been adjusted and the washer 44 and screw 43 fastened to the shaft I4, the tuning mechanism is in operative condition. When set screw 49 is inserted in shank 45, the tuning knob I2 may be rotated so as to tune in a particular broadcasting station. With the parts positioned as in Fig. 4 of the drawings, one of the push buttons I3 is then actuated so that the associated roller 21 moves into engagement with the low part of the cam 29 whereupon the cam 29 has assumed a predetermined position relative to shaft I4 which corresponds to the particular station to which the receiver is tuned. The associated push button I3 is then released and the tuning knob I2 may be rotated so that another station is tuned in. When this has occurred, another cam 29 on the shaft I4 may be moved in the manner described above to a predetermined position differing from the position of the first cam under consideration. This process is repeated until all the cams 29 on the tuning shaft I4 have been moved to different predetermined positions relative to the shaft l 4. The cams 29 are then locked to the shaft I4 merely by moving the tuning knob I2 in an axial direction from the position shown in Fig. 4 of the drawings to the position shown in Fig. 3 thereof. The shank 45 causes the bowed portions of the leaf springs 4! of Fig. 4 to move against the shaft I4 so that the leaf springs become eifectively longer with the resultant compression of the cam stack, the parts of which are moved axially toward the stop member 36. This compression force causes the washers 30 and 3i associated with each cam 29 to lock the respective cams in position. All the cams are locked in position simultaneously with the arrangement described above.

If the screw 43 and the washer 44 are made of insulating material, there is no conducting part of the tunable device extending outside of cabinet I I which may be engaged by an operator whereby the possibility of receiving a shock is completely eliminated. Furthermore, the adjustment or setting of the cams 29 can be accomplished merely by limited axial movement of the tuning knob 52 without the requirement of any additional tools or equipment such as screw drivers or the like. Also, the present invention provides for a very foolproof construction which is simple to assemble and inexpensive to manufacture.

It will be apparent to those skilled in the art that the present invention is not limited to the particular construction shown, but various changes and modifications may be made without departing from the spirit and scope thereof, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

I claim:

1. A control device for a radio receiver including a rotary tuning shaft, a cam mounted on said shaft for relative movement therewith, frictional means for holding said cam in a predetermined fixed position on said shaft, said cam and frictional means comprising a cam stack axially slidable on said shaft, means for limiting the axial movement of said cam stack, a leaf spring positioned adjacent an end of said shaft and having one end thereof engaging said cam stack, means for eifectively fixing the other end of said leaf spring to said shaft so that the center of said leaf spring is bowed away from said shaft, a tuning knob positioned on said end of said shaft for axial movement therewith, and a shank associated with said tuning knob for forcing the bowed portion of said spring against said shaft to compress said cam stack and eifectively lock said cam to sai shaft in response to axial movement of said knob in one direction.

2. A control device for a radio receiver including a rotary tuning shaft, a plurality of spaced cams mounted on said shaft for relative movement therewith, spacing and friction means intermediate said cams, said cams and spacing and friction means comprising a cam stack axially slidable on said shaft, means for limiting the axial movement of said cam stack, a pair of leaf springs positioned adjacent an end of said shaft in diametrically opposed relationship relative thereto and each having one end thereof engaging said cam stack, means for effectively fixing the other ends of said leaf springs to said shaft so that the centers of said leaf springs are bowed away from said shaft, a tuning knob positioned on said end of said shaft for axial movement therewith, and a shank associated with said tuning knob for forcing the bowed ends of said springs against said shaft to compress said cam stack whereby said friction means effectively lock said cams to said shaft in response to axial movement of said. knob in one direction.

3. A control device for a radio receiver includ ing a rotary tuning shaft, a cam mounted on said shaft for relative movement therewith, frictional means for holding said cam in a predetermined fixed position on said shaft, said cam and frictional means comprising a cam stack axially slidable on said shaft, means for limiting the axial movement of said cam stack, a leaf spring positioned adjacent an end of said shaft and having one end thereof engaging said cam stack, means for effectively fixing the other end of said leaf spring to said shaft 50 that the center of said leaf spring is bowed away from said shaft, a tuning knob positioned on said end of said shaft for axial movement therewith, a shank associated with said tuning knob for forcing the bowed portion of said spring against said shaft to compress said cam stack and effectively lock said cam to said shaft in response to axial movement of said knob in one direction, and means for limiting the axial movement of said knob.

RICHARD C. MARI-IOLZ.-

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,122,206 Jennings Dec. 22, 1914 2,200,211 Benton May 7, 1940 2,243,487 Plensler May 27, 1941 

